1. Field of the Invention
The present disclosure relates to OLED, and more particularly to an OLED capable of adjusting the current of the organic layer.
2. Discussion of the Related Art
Usually, OLED includes an anode, a cathode, and a light emitting layer. FIG. 1 is a section view of the conventional OLED. As shown in FIG. 1, the OLED 100 includes an anode 110, a hole injection layer 120, a light emitting layer 130, an electron injection layer 140, and a cathode 150. The cathode 150 is generally made by metallic material, such as Al, and the anode is made by material such as ITO. The operating principles of the OLED 100 will be described below. When the voltage is applied between the anode 110 and the cathode 150, the hole injected from the anode 110 passes through the hole injection layer 120 and arrives the light emitting layer 130. The electrons injected from the cathode 150 pass through the electron injection layer 140 and arrive the light emitting layer 130. The holes and the electrons are composited with each other on the light emitting layer 130 to generate exciton. The exciton is then activated to be at the base state, and then emits lights. Currently, the transparent anode ITO is a majority. That is, the OLED is of the top-emission state. During the manufacturing process, the bottom emission structure is adopted to prevent the organic material from being damaged by evaporated ITO. That is, the light beams are emitted out from the cathode.
When the 2T1C OLED pixel is formed by OLED, the brightness of the pixels may be non-uniform due to being driven by TFTs. FIG. 2 is a driving circuit diagram of the conventional 2T1C OLED pixel. As shown in FIG. 2, the TFT T1 is turned on so as to charge the capacitor (C). The capacitor (C) is configured for turning on the TFT T2 connected with the data voltage (VDD) to drive the OLED to emit lights, which is a constant current source. However, during the driving process, the threshold voltage of the TFT T2 may be shifted. At the same time, the instability of the manufacturing process may result in different threshold voltage of the TFT T2, and the brightness of the pixels may be non-uniform.
To overcome the above problem, the driving circuit of 3T structure has been developed. By adopting the operation amplifier, the input signals may be amplified such that the voltage of the TFT T2 may be affected by the input signals and thus becomes less sensitive, which compensates the non-uniform and instability.